| Quercus lobata | |
|---|---|
 | |
| Valley Oak nearMount Diablo, withmistletoe | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Fagales |
| Family: | Fagaceae |
| Genus: | Quercus |
| Subgenus: | Quercussubg. Quercus |
| Section: | Quercussect. Quercus |
| Species: | Q. lobata |
| Binomial name | |
| Quercus lobata | |
 | |
| Natural range ofQuercus lobata | |
| Synonyms[3] | |
List
| |
Quercus lobata, commonly called thevalley oak orroble, is the largest of theCaliforniaoaks. It isendemic to the state, growing in interior valleys and foothills fromSiskiyou toSan Diego counties.[4]Deciduous, it requires year-roundgroundwater,[5][6] and may live up to 600 years. Its thick, ridgedbark (resemblingalligator hide) and deeply lobed leaves are characteristic, and assist in identification.
The valley oak may surpass 30 meters (98 feet) in height, with a sturdy trunk possibly exceeding 3 m (10 ft) in diameter. The "Henley Oak", inCovelo, California, is the tallest known valley oak, at 47 m (153 ft).[7][8]
The branches have an irregular, spreading and arching appearance. During autumn, theleaves turn a yellow to light orange color but become brown later in the season. In advancing age, the branches droop. The trees have pewter-colored rippledbark.[9]
Typically, the leaves are 5–10 centimeters (2–4 inches) long and are roundly and deeply lobed. The leaf width is approximately one half its length. Each leaf is matte green with an underneath pale green appearance; moreover, the leaf is covered with abundant soft fuzz, yielding an almost velvety feeling. When a fresh leaf is rubbed or broken, anaromatic scent is exuded, evoking a forestodor. The wood is a dull brown approaching yellow.[9][10]
Theacorns are medium to dark brown and range from 2 to 3 cm (3⁄4 to1+1⁄4 in) in length. The caps have deep stippling and are found most often as singlets, but occasionally as doublets. The acorns ripen from October to November.[10] Viable acorns germinate in their first winter, and none remain by mid-winter.
Valley oak is of thewhite oakevolutionary lineage, which is officially known as the sectionQuercus insubgenusQuercus. This section comprises numerous oaks from California and elsewhere, which species share similar leaves, acorns, bark andwood pulp. Earlysettlers used a variety of common names for the valley oak including: white oak, bottom oak, swamp oak, water oak and mush oak. TheSpaniards, because the tree looked like the white oaks in Europe, called the tree "roble".
TheConcow tribe call the acornslō-ē' (Konkow language).[11]
Valley oak tolerates cool wet winters and hot dry summers, but requires abundant water. It is most abundant in rich deep soils of valley floors below 600 meters (2000 feet) in elevation. Valley oak is found in denseriparian forests, openfoothill woodlands and valleysavannas. Commonly associated trees arecoast live oak,interior live oak,blue oak,California black walnut,California sycamore andgray pine.[12]
The valley oak is widely distributed in: the CaliforniaCentral Valley; many smaller valleys such as theSan Fernando Valley (original Spanish place-name fromoak savannah),Santa Clarita Valley,Conejo Valley, andSanta Ynez Valley; theInner Coast Ranges south of theEel River; and theTransverse Ranges from theTehachapi Mountains to theSimi Hills,Santa Susana Mountains. It is also present onSanta Cruz Island andCatalina Island in thePacific Ocean. Some of the most picturesque stands are found inSonoma Valley, Round Valley inMendocino County and the southernSalinas Valley near the up-river reaches of theSalinas River.[4][12]
Like many oaks, valley oaks can tolerate wildfires. Although smaller individuals may be top-killed, most resprout from the root crown.[13]
A variety ofmammals andbirds eat the acorns, including theacorn woodpecker,California scrub jay,yellow-billed magpie, andCalifornia ground squirrel.[10] The acorns are also attacked bybruchid beetles, but can survive moderate levels of infestation.[14]
Globulargalls are frequently attached to twigs of mature specimens of valley oak. These house thelarval stage of small indigenouswaspsAndricus quercuscalifornicus. A related wasp species,Feron kingi, produces small red conical galls on leaf surfaces. The valley oak is the only known food plant ofChionodes petalumensis caterpillars.
Theacorns are sweet and edible; Native Americans including theSouthern Paiute people roasted them and ground the edible portion into meal to make into bread and mush.[15][16]
Difficulties in acquiring valley oak wood as well as issues stemming from its drying such as cracking and warping have shifted its consumption from a general purpose lumber to a primarily niche product.[10] Valley oak wood has a small, but significant market for use in cabinetry though, and is also suitable for hardwood flooring.[10]Tyloses present in the pores of valley oak wood increase its impermeability to fluids allowing it to be used in the production of water-tight vessels.[10] Such vessels include wine barrels where valley oak wood sees limited role in the composition of and where it has similar properties to otherwhite oaks such as a reduced tannin load compared to thered oaks and an open grain that allows for an increased transfer of oxygen.[10]
In 1792, the English explorerGeorge Vancouver noted on his expedition through theSanta Clara Valley, after seeing an expanse of valley oaks:
For about twenty miles it could only be compared to a park which had originally been closely planted with the true old English oak; the underwood, that had probably attended its early growth, had the appearance of having been cleared away and left the stately lords of the forest in complete possession of the soil which was covered with luxuriant foliage.[17]
In the year 1861,William Henry Brewer, the chief botanist for the firstCalifornia Geological Survey wrote of the valley oaks that he saw inMonterey County:
First I passed through a wild canyon, then over hills covered with oats, with here and there trees—oaks and pines. Some of these oaks were noble ones indeed. How I wish one stood in our yard at home....I measured one [valley oak] with wide spreading and cragged branches, that was 26.5 feet in circumference. Another had a diameter of over six feet, and the branches spread over 75 feet each way. I lay beneath its shade a little while before going on.[17]
TheHooker Oak ofChico, California, was once considered the largest-known valley oak. When it fell on May 1, 1977, it was nearly 30 m (100 ft) and 8.8 m (29 ft) in circumference at 2.4 m (8 ft) from the ground.
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